The Common Cold: A Note Regarding Isolation of an Agent

Abstract

Nasal washings in sterile skimmed milk were taken from a subject 24 hrs. after onset of cold symptoms. The un-filtered washings were given intranasally to 5 volunteers in previously strict isolation. After 36-48 hrs., all 5 developed a minor upper respiratory infection. They complained of fatigue, nasal obstruction, expectoration, and there were hyperemic obstructed nasal passages, red throats with enlarged lymphoid follicles, and large amts. of postnasal mucus for 2-5 days. Slight temp. rises occurred. Nasal washings in sterile skimmed milk, taken from one volunteer with the most severe symptoms, were inoculated into embryo-nated hens'' eggs with 1,000 U. of penicillin and 100 U. of streptomycin. A large number of deaths of embryos occurred after 2 passages by way of the allantoic cavity. The fluids from these were bacteriologically sterile, and several substrains were established. One substrain was tested in the 4th passage in man and caused a mild illness similar to that affecting the original volunteers. No disease was produced by fluids from the 5th egg passage. A 2d substrain was passed blindly and after 8 passages allantoic fluids failed to produce disease. A 3d substrain was run through 4 passages, transfers being made from the 5th to the 7th day following inoculation. Some embryos died in the 3d to the 5th days. After the 4th passage, allantoic fluid caused mild coryza and mild temp. elevation. Two substrains from this fluid produced similar upper respiratory infections in all of 14 volunteers. Their illness was severe and of long duration. Sixth-passage allantoic fluid produced a moderately severe upper-respiratory infection in 15 of 16 volunteers; 7th-passage fluid produced a similar condition in 14 of 16 subjects. Of 60 individuals so far tested, 57 have developed a characteristic clinical picture that has been consistent. The exact nature of the agent has not been defined. The material has not produced symptoms in mice, hamsters, rats, cotton rats, guinea pigs, and rabbits. Allantoic fluids did not agglutinate chicken red cells, and volunteers showed no rise in antibody to influenza A or B. The material maintains its infectiousness for several weeks when rapidly frozen at[long dash]70[degree]C and stored at[long dash]50[degree]C. Electron microscopy has shown characteristic particles in some active prepns. which have not been seen before in prepns. from normal allantoic fluids or from fluids of eggs inoc. with normal fluids. These particles are of the same size as influenza viruses but are not like them.